Počet záznamů: 1  

The late Aeronian graptolite .i.sedgwickii./i. Event. Associated positive carbon isotope excursion and facies changes in the Prague Synform (Barrandian area, Bohemia)

  1. 1.
    0381216 - GLÚ 2013 RIV GB eng J - Článek v odborném periodiku
    Štorch, Petr - Frýda, J.
    The late Aeronian graptolite sedgwickii Event. Associated positive carbon isotope excursion and facies changes in the Prague Synform (Barrandian area, Bohemia).
    Geological Magazine. Roč. 149, č. 6 (2012), s. 1089-1106. ISSN 0016-7568. E-ISSN 1469-5081
    Grant CEP: GA ČR GA205/09/0619
    Výzkumný záměr: CEZ:AV0Z30130516
    Klíčová slova: carbon isotope record * community evenness * extinction * graptolites * Silurian * species richness
    Kód oboru RIV: DB - Geologie a mineralogie
    Impakt faktor: 2.270, rok: 2012

    Lower Silurian black-shale succession of the Prague Synform provided detailed insight into graptolite faunal dynamics and diversity trends from middle Aeronian diversity maximum through late Aeronian crisis. Graptolite diversity decreased from 33 taxa in the Lituigraptus convolutus Biozone to 17 taxa in the upper part of the Stimulograptus sedgwickii Biozone and newly erected Lituigraptus rastrum Biozone. The graptolite assemblages of the latter biozones exhibit low species richness along with high dominance. Many graptolite species that became extinct in the early part of the sedgwickii Zone were promptly replaced by new forms. In the later part of the sedgwickii Zone, however, replacement of extinct species by new forms considerably decelerated. The increased rate of graptolite extinction in the convolutus-sedgwickii zone boundary beds coincided with subtle changes in black shale lithologies and a positive shift in δ13Corg (for 2.2 >) compared to baseline values. Sea-level drawdown can be inferred from silt sedimentation and/or temporary nondeposition in the middle of the sedgwickii Zone. Middle part of the sedgwickii Zone sees also TOC fluctuations and strong positive δ13Corg excursion with peak shift at least 7 >. Still elevated values of δ13Corg returned to baseline values in the course of the rastrum Zone. The sedgwickii Event exhibits substantial reorganization of the graptolite fauna, its taxonomical impoverishment and concomitant increase in species dominance rather than sudden collapse of the pre-extinction assemblage. Associated changes in lithology, TOC and strong δ13Corg excursion suggest a relatively extended and probably multi-phase period of stress conditions which affected the pelagic realm inhabited by graptolites in the course of the late Aeronian interval. Aeronian-Telychian boundary is drawn in pale-coloured barren mudstone which separated black shales of L. rastrum and Rastrites linnaei biozones.
    Trvalý link: http://hdl.handle.net/11104/0215975

     
     
Počet záznamů: 1  

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